1. Field of the Invention
The present invention relates to image distortion correcting mechanisms of back-projection image display devices and back-projection image display devices.
2. Description of the Background Art
In a back-projection image display device in which image light outputted from a projection device is reflected by a reflection mirror and projected onto the back of a screen, an image displayed on the screen can be adjusted by adjusting the position of the projection device using a position adjuster (six-axis adjuster). For example, an image displayed on the screen can be moved vertically and horizontally, rotated, and zoomed in or out. Vertical trapezoidal distortion and horizontal trapezoidal distortion that cause an image which should be a rectangle to become an isosceles trapezoid can also be corrected.
However, such image adjustment using a position adjuster cannot correct pin distortion that causes an image which should be a rectangle to be shaped like a pincushion or barrel distortion that causes an image which should be a rectangle to be shaped like a barrel, which occur due to the characteristics of a projection lens and distortion of a reflection mirror. Trapezial distortion that causes an image which should be a rectangle to become a trapezium cannot be corrected either.
For this reason, attempts have been made to correct these types of image distortion by deforming a reflection mirror in a back-projection image display device. By way of examples, Japanese Patent Application Laid-Open No. 2002-077777 discloses a technique of correcting pin distortion and barrel distortion by deforming a reflection mirror, and Japanese Patent Application Laid-Open No. 2004-309529 discloses a technique of correcting trapezial distortion by deforming a reflection mirror.
However, the back-projection image display devices of JP 2002-077777 and 2004-309529 are problematic because their image adjustment operations are not easy. For example, when one operator engages in the image adjustment, the operator has to leave the back-projection image display device to check an image displayed on the screen each time an adjustment is made to the image in the display device. To avoid such troublesome effort, two operators have to be kept for the image adjustment.
This problem becomes noticeable particularly when adjusting an image in order to join the connecting point of images displayed on adjacent screens in an image display device having a combination of a plurality of back-projection image display devices.